The primary objective is to determine whether levodopa slows or hastens the progression of PD by conducting a placebo-controlled, randomized, double-blind clinical trial. Not only is this an important scientific question, it also is one of immense practical clinical importance. If the answer to this question is that levodopa does not hasten worsening of PD, then physicians would utilize levodopa earlier in the course of the illness rather than delaying its introduction until disability threatens, which is the current practice of most neurologist. If the answer is the opposite, then physicians would more aggressively employ levodopa-delaying, levodopa-sparing, and levodopa-avoiding strategies. Thus, the knowledge from this study will have a major impact on the treatment of PD.